1. Field of the Invention
The present invention relates to a method for quantitatively determining the expression of a gene.
2. Description of the Prior Art
In order to determine the level of a gene expression, generally, Northern hybridization is carried out. For the routine determination at the laboratory level, the presence of 5 pg (picograms) of RNA is sufficient for detection. However, in cases where the amount of expression of a target gene is extremely small, 0.3-3 .mu.g of mRNA is required for detection. Thus, it is difficult to apply Northern hybridization to cases where samples of limited amounts are only available (e.g., clinical samples).
Polymerase chain reaction (PCR) is a technique by which DNA or RNA can be detected most sensitively compared to other techniques. However, quantitative determination of a gene expression by PCR involves a control experiment in which a calibration curve is prepared using, as the so-called "internal control", a DNA fragment having an amplification efficiency similar to that of a target molecule. Thus, operations are complicated. Furthermore, in order to perform a quantitative PCR, it is necessary to prepare a calibration curve for each of the target genes to be quantitatively determined. Thus, a study of genes or a genetic diagnosis with this method requires much time and labor.